( 1)NR
NR is nonpolar rubber. Although it has excellent comprehensive properties, its oil resistance, organic solvent resistance, thermal oxidation resistance, ozone aging resistance and ultraviolet resistance are poor, which limits its application in some special occasions. The application range of natural rubber can be greatly expanded by modification.
A) epoxidized natural rubber (ENR)
Epoxidized natural rubber (ENR) is a special natural rubber chemically modified from natural rubber (NR). Compared with NR, ENR has completely different viscoelastic and thermodynamic properties, such as excellent air tightness, adhesion, wet skid resistance and good oil resistance. ENR can be firmly combined with polar fillers (such as silica), and ENR vulcanizate can still maintain the high modulus and tensile strength of NR without fillers. ENR 50 has good oil resistance and damping. When it is used in tire tread compound, the strong interaction between ENR and silica is an important factor to improve the comprehensive performance of rolling resistance and wet grip without coupling agent. When ENR25 is mixed with silica/carbon black filler, the best wear resistance can be obtained.
B) grafting natural rubber
At present, methyl methacrylate (MMA) grafted NR is the most studied. MMA grafted NR has high elongation, high hardness, good impact resistance, bending crack resistance, dynamic fatigue performance, adhesion and good filling property. It is mainly used in manufacturing elastic products with good impact performance, such as the inner lining of tubeless tires. If it is used together with styrene-butadiene rubber, it can be used as bead triangle rubber compound, and its green rubber strength and adhesion to traveler are obviously improved, and the stiffness of traveler is increased, and the shape of traveler remains stable.
The new development of isoprene is the synthesis of 3,4-polyisoprene rubber (high glass transition temperature). This kind of rubber can be used with natural rubber, styrene-butadiene rubber and polybutadiene rubber to improve the grip performance. Polymers of isoprene and butadiene have been successfully developed, and trimers of isoprene with styrene and butadiene have also been successfully studied. The tread rubber made of these rubbers has a good comprehensive balance between rolling resistance and wet road grip.
China patent ZL95 1 10352.0 introduces a new technology of directly synthesizing trans-1, 4- polyisoprene (TPI) powder by bulk precipitation polymerization of isoprene catalyzed by supported titanium. It is reported that 20-25 parts by weight of TPI is used to replace cars and light semi-steel radial tires made of styrene-butadiene rubber, which has achieved good comprehensive driving performance and reduced fuel consumption by about 2.5% in the fuel consumption test of 100 kilometers.
(2)IR
The new development of IR is 3,4-polyisoprene rubber (high glass transition temperature), which can be used as tread rubber with NR, SBR and BR to improve the grip of tires. At present, polymers of isoprene and butadiene and trimers of isoprene, styrene and butadiene have been successfully developed, which can make tires have a good comprehensive balance of rolling resistance and wet grip when used as tread rubber. China invention patent (ZL 95 1 10352. A new synthesis process of trans-1, 4- polyisoprene (T PI) powder was introduced. The comprehensive performance of radial tires for cars and light trucks produced by replacing styrene-butadiene rubber with 20~ 25 phr TPI in tread rubber is good, and the fuel consumption is reduced by about 2. 5%.
(3)SSBR
Solution polymerized styrene-butadiene rubber (SSBR) is widely used in green tire tread, and special varieties with different macro-structure, micro-structure and chain end modification can be produced as required. In the process of polymer production, adding some chemicals can change the end of polymer chain, significantly enhance the interaction between polymer and carbon black, reduce the interaction between fillers, and thus reduce the rolling resistance of tires.
The third generation SSBR improved the comprehensive properties of rubber to the maximum extent through the optimization of molecular design and chain structure. There are three main products: First, styrene-isoprene-butadiene * * * polymer made by introducing isoprene segments into the macromolecular chain, that is, integrated rubber (SIBR), which combines good low-temperature performance, low rolling resistance and high grip, and is by far the most comprehensive diene synthetic rubber. Secondly, the blocky SSBR with gradual sequence structure distribution can balance the wet sliding resistance and rolling resistance well; Thirdly, SSBR modified by silane enhances the affinity between rubber and white reinforcing agents such as silica, and expensive coupling agents such as titanate can be omitted or used less when matching. This kind of environmental protection product can meet the increasingly stringent environmental protection requirements and conform to the development direction of modern tires.
(4)BR
Automobile tires must balance the magic triangle of rolling resistance, wear resistance and wet skid resistance as much as possible. High cis BR can not only solve the problem of tread wear resistance, but also play its advantages in other parts of the tire. The combination of BR and SSBR as tread compound can make the tire have the best comprehensive balance of grip and wear, reduce rolling resistance and save fuel by 5%. BR/ SSBR tread rubber adopts silica and silane coupling agent. When the dosage of BR is increased to 40 phr, the wear resistance can be maintained, while SSBR and silica can reduce the rolling resistance and improve the traction of tires on snow and wet roads. BR The most used part is the sidewall of radial tire. The NR/ BR blend with antioxidant 6PPD (blending ratio 50: 50) has the best crack propagation resistance, good puncture resistance and long service life. BR can improve wear resistance and elasticity, and reduce fever. The combination of high vinyl content cis-polybutadiene rubber (HVBR) and natural rubber can improve the aging resistance and vulcanization reversion resistance.
(5)IIR
The main application field of IIR is tires, accounting for more than 80% of its total consumption. With the development of tubeless tires, the demand for HIIR is increasing year by year. At present, the demand for HIIR has accounted for about 60% of the total demand for IIR. IIR has excellent air tightness and chemical resistance.
(6) Foamed rubber
In order to solve the dust problem caused by diamond-encrusted tires, diamond-encrusted tires were replaced by anti-skid tires. An important feature of studless anti-skid tires is high friction at about 0 degrees Celsius. On wet ice, it is necessary to greatly improve the drainage effect, and it is not enough to rely solely on the drainage effect of grooves and sipes. At present, a new type of rubber has been developed, which can improve the drainage, meshing effect and adhesion friction, and the representative is foamed rubber. Foamed rubber refers to rubber with many tiny independent bubbles.
(7) Polyurethane elastomer
Compared with rubber, polyurethane elastomer has better wear resistance, higher tear strength and wider hardness range. Pouring polyurethane elastomer is the most wear-resistant elastomer at present, which has high wear resistance, coloring, cutting resistance, excellent oil resistance and chemical resistance, has no toxic effect on human body, and can be completely biodegradable without adding carbon black and aromatic oil. It is an ideal material for tire tread. Michelin's PAX run-flat tire is equipped with a brand-new lightweight polyurethane auxiliary support ring, which is about 4 kg smaller than the original rubber support ring. The key technology of using polyurethane as tire retreading material is to improve the thermal stability of polyurethane elastomer through nanotechnology, so that its maximum service temperature can reach 120 degrees Celsius. Secondly, the rubber surface treatment agent and adhesive with low cost, convenient use and good effect were developed, so that the polyurethane tread was firmly bonded with ordinary rubber. The actual mileage of polyurethane tread retreaded tires is 1~ 2 times higher than that of ordinary tires, and at the same time, it can eliminate the environmental pollution caused by a lot of carbon black and aromatic oil, which is a new way to improve the performance of retreaded tires. (1) rayon
Rayon is often used in high performance tires and run-flat tires because of its good dimensional stability and excellent handling performance. However, people pay more and more attention to the problem that rayon consumes natural forest resources and the production process is seriously polluted.
(2) Nylon
Nylon cord is mainly used for bias tires, and the latest new products are poly (hexamethylene adipamide) fiber and HYTEN high strength polyamide fiber from DuPont. Polyhexamethylene diamine fiber (nylon 46) has the characteristics of high melting point, small thermal shrinkage and high modulus, and unlike nylon 6 and nylon 66, it is not easy to melt the cord due to heat, which reduces the durability of the tire. Using Haiteng as the carcass skeleton material of radial tire can make the tire have good durability and low heat generation, and reduce the tire weight. The aviation tire trial-produced by Goodyear Company with large diameter HYTEN cord as buffer layer and carcass ply can reach about 65,438+07% and 45% respectively, which can reduce the standing wave phenomenon, shear deformation and heat generation of the ply.
(3) polyester
Polyester is one of the steadily developing fibers in rubber industry. In 1980s, dimensionally stable polyester (DSP) was successfully developed. Using polyester cord fabric with stable size to make radial tire can avoid the inflation process after vulcanization and solve the appearance problem of sidewall depression caused by thermal shrinkage. The raw material cost of polyester for light truck tires is 35% lower than that of rayon. Because the strength of polyester is higher than rayon, the number of carcass layers can usually be reduced when polyester is used.
(4) Steel wire
The biggest feature of steel wire is its high strength. In recent years, the main new products of steel wire skeleton materials for tires are as follows.
A) high strength steel wire
In recent years, high-strength steel cord has been widely used in tires, and its strength is 20% ~ 40% higher than that of ordinary steel cord. At present, the strength of ultra-high strength steel wire is up to 4. 0 GPa is still under development.
B) ultra-fine and super-strong steel wire
Goodyear Company has specially developed ultra-fine and super-strong steel wires for run-flat tires (7 000 steel wires can be arranged within 25 mm). The successful development of this superfine steel cord initiated the application of steel cord in automobile tire carcass.
(5) Aramid
Aramid fiber has high thermal stability, oxidative degradation at 400~ 430 degrees Celsius, melting point as high as 500 degrees Celsius and high modulus.
(6) Composite cord
Up to now, there is no commercially available cord that can fully meet the various properties required by tires. In order to make full use of the advantages of various cords and overcome their disadvantages, people put forward the method of adopting composite cords. The existing patent proposes to make nylon/polyester composite cord with nylon filament as the surface layer and polyester filament as the core layer, which combines the elasticity and strength of polyester cord and the good adhesion of nylon cord. Compared with aramid cord, the composite cord made of 1~ 2 strands of aramid and 1 strand of nylon or polyester has the following characteristics: higher fatigue resistance and elongation at break, lower modulus, controllable shrinkage and better or equivalent strength/cost ratio. Compared with aramid/nylon composite cord, aramid/polyester composite cord has slightly lower tensile properties, much higher modulus, less permanent deformation and poor adhesion. At present, some large construction machinery tires have adopted composite cords. In recent years, new fillers such as high-structure carbon black, nano-structure carbon black, silica and carbon black-silica dual-phase filler have been successfully developed. On the premise of keeping the rolling resistance of tire tread rubber low, the wear resistance of tire is improved, the comprehensive performance of tire is improved, and the development of green tire is promoted.
(1) carbon black
A) carbon black with high performance and low hysteresis loss
High performance carbon black is characterized by small particle size, suitable structure, narrow aggregate particle size distribution and high surface activity, while low hysteresis loss carbon black is characterized by high structure, wide aggregate particle size distribution and high surface activity.
B) nanostructured carbon black
Nanostructured carbon black is produced by an improved furnace method. Compared with traditional carbon black, nanostructured carbon black has higher surface roughness and activity. The higher surface activity is mainly related to the smaller crystalline particles with highly disordered cross-linking. This crystalline particle has a large number of edges and becomes an active field with high surface energy, which has strong interaction with polymers.
(2) white carbon black
Silicon dioxide is a highly dispersed amorphous powder or flocculent powder with high electrical insulation, porosity and water absorption. Its original particle size is less than 3? M, so the specific surface area is large. Tread adopts special polymer and silica/silane system, which can obtain high wet traction performance and wet braking performance and reduce rolling resistance. In the European original car tire market, the number of tires with silica/silane filling system has reached more than 80%. The great improvement of modern winter tire performance mainly depends on the use of silica/silane system in tread compound. Special high dispersion silica combined with high structure fine particle carbon black used in truck tires can reduce rolling resistance while maintaining wear resistance.
(3) carbon black-silica dual-phase filler
Carbon black-silica dual-phase filler improves the interaction between elastomer and filler, but reduces the interaction between filler and filler, which can greatly reduce the rolling resistance of tire and improve traction without reducing the wear resistance of traditional carbon black [20].
(4) A new starch-based filler (BoT red)
BoT red is a new filler based on starch. Firstly, corn starch derivatives are extracted from corn, which are converted into droplets, and then processed into biopolymer fillers. BoT red is spherical particles, which is convenient to minimize mechanical energy and reduce rolling resistance. Compared with the previous generation products, the GT3 green tire manufactured by Goodyear Company with BoT red has improved water sliding resistance by 5%, reduced weight by 100 g and reduced rolling resistance by 10%.
(5) Short fiber
The influence of short fiber applied to tire tread on tire rolling resistance mainly includes the following two aspects: a) improving the rigidity of tire, so that the subsidence of tire under the same load during driving is obviously reduced, that is, the deformation of tire is reduced, thus reducing rolling resistance; B) The use of short fibers in the tread compound can not only improve the rigidity of the tread, but also reduce the friction coefficient and rolling resistance of the tread accordingly.